Woodburn May 15

Yes, I have been quiet lately. I am very sorry about that. One day leads to another always busy, then before I know it another week or month has passed and I still haven’t updated my blog. So now it is time for me to get back at it.

This season is still a little unknown for me at this point. In mid April I finally got Dennis Hicks’ car into my shop to update the driver’s compartment, install a new clutch and trans, and sort out the trouble I was having with the steering all last season. Unfortunately once I got it here I discovered that my steering problem was a result of the chassis being out of alignment by about 3 and a half inches. Most of the trouble appeared to be in the rear axle housing. Add to that the engine being way out of alignment with the pinion. (no wonder the rear trans seal was always leaking).  The good news is that the shop that built the car in the first place said they would make it right, so Dennis took the car back up to them to have it made right. Because the work I had to do was all based on and around the rear axle and bellhousing there was nothing I could effectively do with the car until the alignment issues were resolved. At this point I am not sure of the status of the car. I am a big believer in checking the car immediately after the race event, or race season, not immediately before the race event or race season, that way there is plenty of time and resources to make any required repairs properly.

I was sad to not be able to make it to the opening event in Ashcroft this last weekend, but very happy to hear that it all went well for everyone. I was in Woodburn Oregon with Bill Edwards racing. I will be helping Bill and his son BJ, (Bill Junior) with their Top Alcohol Dragster operation this year, and be doing a bit of driving for them as their schedule allows. We are hoping to have the car in Ashcroft with me driving for the AHRA Reunion tour event in August.

I made one attempt at a half track pass in the car on Saturday. It wasn’t very pretty. In hindsight I should have made more adjustments in the driver’s compartment, I didn’t have the clutch control I should have had, which resulted in no burnout. Add to that a little more horsepower in the motor than Bill was expecting and the car went straight into wheelspin on the launch, then into some pretty violent tire shake. I poked second gear hoping it might settle down, but it didn’t.

On Sunday BJ took over the controls as planned. Unfortunately he didn’t fare much better, with bad tire shake breaking the tires free on the first run and breaking a fuel line on the second run. We are certainly hoping for much better results in Mission in two weeks.

I have a few photos from the weekend which I will post up in a couple days. One great shot of what bad tire shake looks like.

While I was in Woodburn I was able to catch up with Darin Bay, whom I met at the BC Classic and Custom car show earlier this year. He was there with his two jet dragsters and was doing double duty driving Twig Ziggler’s Nostalgia funny car as well. There is a Jet funny car owner in this area who is still talking about getting me to pilot his car, so I catch up with the jet cars whenever I can. They really do put on a fantastic show. I was able to watch one of Darin’s runs from the top end on Sunday, it is absolutely amazing how fast those things are accelerating from about 800 feet onwards. They are just starting to really get going when they have to be shut down. . . I wonder how fast they could go on a half mile run? . . .

Questions

I see many people coming to my site from Google or other search engines. Theses people are asking questions. Questions like: Why does my ladder bar car turn left when I launch? What is the correct pinion angle for a dragster? How to pre-load a rear suspension? and similar.

I have tried to sit down and answer these questions in a blog post as they come in, but I have found that the articles become almost huge as there are so many variables that need to be addressed.

I have an idea.

I encourage you to ask  your question directly to me. You can email me through the contacts page at the back, and I will reply, most likely with more questions so I can answer your question as it pertains to your needs.

I have many customers who email me with all sorts of questions, they send me photos and specs and I guide them through the process they are trying to accomplish. The cool thing about this sport is it is hands on, most of you guys and girls build the car, and set it up yourself. That is fantastic, and if I can help I am more than happy to.

So, don’t be shy or embarrassed, ask away, and I will respond in a timely manner, (you won’t be waiting a week for a reply). You can ask anything to do with Drag racing, from chassis design and setup, engine building and tuning, gas, alcohol, and nitro, gear ratios, tires, driving techniques, sponsorship, or rules, or any thing else.

Pinion Angle.

Magic is an interesting concept. If we look back through the ages at things which were not understood at the time, they were often referred to as magic. Pinion angle is a term I hear tossed about as some sort of magic incantation quite often. Let’s dispel the myth.

Pinion angle in and of itself does not affect the way a car launches. A change in pinion angle does change the angle of the four link or ladder bar brackets on the rear axle housing. So a change in pinion angle will change the angle of push and pull on your rear suspension components, but, and this is the important part, we do not want to use pinion angle as a rear suspension tuning aid.

What we do want to do with pinion angle is have the drive-line in the right relationship so the universal joints work correctly.

Universal joints; this is really cool. Picture a simple shaft, now add a single universal joint in the middle of it and bend it slightly. You can now rotate one end of the shaft, and the other end of the shaft can also rotate, even though it is, in effect, going around a corner. (that’s not the cool part) If you could rotate the input end of the shaft at a very accurate constant velocity, and if you could accurately measure the velocity of the output shaft as it rotates, you would find that the output shaft does not rotate at a constant velocity. In fact through one revolution it actually speeds up and slows down several times as each cross of the universal joint changes angle, even though it still completes one revolution in the same amount of time as the input shaft.

The amount of this acceleration and deceleration changes with the angle of the universal joint. (you can see where I am going with this already can’t you?) From there it is pretty simple to visualize what we might want from a driveshaft with two universal joints in it, we would want both joints to accelerate and decelerate the same amount, at the same time, if we do not, we end up with vibration. We will not always feel the vibration in a drag car that is accelerating, but it is tearing up universal joints as they fight each other. So, pretty simple, we want both universal joint angles to be the same. Mark Williams has a great drawing here to show what I mean.

Now comes the bit that seems to be magic, we want the universal joints to operate at the same angle. . . when the shaft is turning.

Generally if the car has universal joints, it has suspension, suspension allows movement, which will change the angle of the u-joints, so we need some sort of compromise. Logic says we would want our universal joints to be operating at the same angles when they are under the greatest load. Which in our case is when we launch the car. If you remember back to a previous installment, when we launch the car, the rotation of the pinion gear on the ring gear causes the rear axle housing to rotate around the axles in the opposite direction of the tires. Put simply the front of the axle housing wants to go up, the front where the pinion goes in. . . the pinion that is on the end of the driveshaft. . .  after the universal joint. So we will want to take this movement into account when we are setting our pinion angle.

So now, when you are setting up your pinion angle on the floor of your shop, you want to add a little to the angle to compensate for the rotation of the rear housing when you accelerate, here it comes that number you have heard, two degrees down. Ok, two degrees is not always the “exactly” correct angle, but it is a good starting point. but this does not mean that your pinion is set to two degrees, what you want is two degrees more to compensate for rear axle housing rotation. Let’s refer the the Mark Williams drawing here. If Angle “B” is ten degrees, you would want angle “A”, at the pinion, to be pointed down a little to compensate for torque reaction during launch, (the rotation of the front of the axle housing upward), so angle “A” should be about eight degrees. Of course the number itself is dependent on where you measure the angle, but let’s put it simple, you want the pinion pointed down about two degrees more than the back of the transmission. Of course this is all at ride height with fuel load and driver weight in place.

I think one place where many go wrong with the whole pinion angle deal is they do not correct pinion angle after they adjust the rear suspension. Particularly with ladder bars, if you change the front mount location, you must correct your pinion angle.

Ladder Bar Setup. Part one, center and square.

Ok, everyone seems to want to know how to setup their ladder bars, so I will see if I can shed some light on the subject. For those of you with four links. . . work it out yourself. No, no, I promise, I will do four links too, but they are a little more involved, and in effect build on the ladder bar principles, so I will start with ladder bars, and do four links at a later date.

I have given a lot of thought to how to approach this. I have decided that I will try to keep away from the engineering and physics as much as possible, and try to make this a “practical” guide. This is aimed at what I would consider the average bracket racer, with basic understanding, and tools.

First, you need a mostly level surface. Ok, here it comes already, the ‘experts’ out there are going to tell me it has to be perfectly level. Yes, perfectly level would be nice, but tell me this; how level is the startline at your dragstrip? Do you even know?  If you want ideal, you will set your car up on the startline, and the lane, of the track you are about to race on. That is most likely not possible, so we will settle with mostly level. Dragstrip startlines are generally pretty good, some much better than others. They usually have a very slight amount of camber to the outside for drainage, which is why you always start your burnout a little to the inside right? I will assume you are using your garage or workshop floor to work on here. To get mostly level, put the car in nose first, and centered in the doorway. The floor will usually have some drainage built into the floor so liquid will drain out. By nosing the car in, it puts the front end on the high side, more like a wheels up launch, and centering the car should have it pretty close left and right. What you want to do now, is make some marks on the floor, or take some measurements, so you can park the car in the same spot in the future to get the same results. You will want a reference of some sort.

Next, you do want some weight on the driver’s seat to simulate the driver. It does make a difference. You know how much you weigh, add that amount. Within twenty pounds is fine. Set your tire pressures to where you would normally run the car.  Now you get to get dirty.

The very first step is to square the axle in the car. And see, it is already getting tricky. What will you square it to? Is the chassis square? No sense squaring the axle to the rear cross-member  if the cross-member was installed out of square, how will you ever know? Let’s triangulate. No, it is not physics, it’s geometry.

Head up to the front end, at the front cross-member, between the front wheels, measure the distance between the front wheels, this can be inside to inside, or to straightedges held on the outside by your assistant, whatever is easiest, but be accurate, a sixteenth of an inch accurate. If you are measuring from the wheel or the tire spin the wheel an measure from a couple different points to make sure you are getting consistent measurements. Take that measurement, find the middle, the exact middle, and make a lark on your front cross-member at this distance. Sometimes I will use a plumb bob and drop points to the floor, or use a carpenter’s square. Once I have a mark in the centre of the front cross-member I am confident is in the exact centre of my front wheel track, I will make a permanent mark, usually a centre punch mark, then it is always there. When I am building a car I mark it while it is still on the jig. Now you have the centre of the front. Perfect.

Next. To use this procedure to square the rear axle, you need the rear axle to be centered in the car. The best bet is to center to the chassis, as the body may be a little offset. From under the car, measure from the inside of the tire or wheel, to the chassis rail where it goes up and over the rear axle. Sometimes it is way too tight  to get in there, in that case you will have to pull the wheels off  to get this measurement.  So now you find your rear axle is half an inch offset one way or the other, not at all unusual. Sometimes it is less, sometimes more, but we can fix it. You will most likely have a panhard bar, or a wishbone setup to center the housing. Loosen the jam nuts and adjust the housing from side to side. A wishbone is a little more involved as you will have to remove the bar from the brackets to make the adjustments. Another note on the wishbone, if you wind one rod end in, wind the other one out the same number of turns to keep the width the same so you can get the bolts back in. (a little pet peeve of mine, the rod ends should be parallel). If any of your rod ends are difficult to turn, remove them from the car, clean the threads, inside and out, spray some good oil up inside the tube, (I use engine store fogging oil) to prevent corrosion, and grease the threads. I don’t use never seize, it is dirty and abrasive, I use good quality grease. Now next time you need to make an adjustment, there will be less cursing.

Back to squaring the axle in the car. Ok, now you have the rear axle centered between the rear chassis rails, and a center mark on the front cross-member. The next step is to choose a point on the ends of the rear axle to measure forward to the front cross-member center mark. You can use the front edge of the brake drum, or disc, the backing plate, or the backing plate flange. The important thing is to use the same spot on both sides. measure from your chosen point to the center mark on your front cross-member, (again you can use a plumb bob, or carpenter’s square to drop marks onto the floor if it makes things easier). The objective here is to have the dimension the same on both sides, right rear brake drum to front cross-member center the same distance as the left rear brake drum to front cross-member centre. Again, be as accurate as possible, a sixteenth of an inch or better.

They’re not the same are they. That means one rear wheel is further forward than the other. Now it is time to look at your ladder bars and see if one is adjusted longer or shorter than the other. What we are concerned about here is the bottom of the bar, we will use the top to adjust pinion angle later, but for now we want the axle square. I generally start by removing the ladder bars, remove and inspect all the rod ends, and the bars themselves for any damage, rust, cracks etc. Lubricate everything, and assemble the bars with all adjustments in the middle of their range, (which is about six threads showing on the rod end). Before re-installing the bars I will adjust the bottoms to the same length, if the chassis is all square and true, the housing will be square. Back to your car, if you have adjustable ladder bars, set the adjusters, (which are normally on the bottom and rear of the bar) in the middle of their adjustment range, and adjust the front of the bar, the front rod end, to square the housing in the chassis, to make both dimensions from the rear brake drum to the front cross-member center mark equal. Ideally you want both front rod ends in or out of the tube the same amount, and preferably with about six threads showing, (that is above the jam nut). A couple threads either way is not too bad. If you are finding that you have to have much more difference than that, either your housing or chassis brackets are on crooked, or your chassis is crooked. I am going to assume that everything is pretty close.

Now you have a rear axle that is centered, and square in your car.

A brief overview:

Car mostly level.

Find the center of the car at the front.

Center the rear housing in the chassis.

Measure from either end of the rear housing to the front center mark to square the housing in the car.

See, this is easy.

Next we get to talk about pinion angle.

Weekend update

Was it cold in Ashcroft!

Well this weekend was disappointing on one level, but a whole lot of fun on another. As you know I was supposed to be running the 1936 International pickup retro rod from Boomers this weekend but unfortunately it was not to be. The mechanical gods figured I had had more than enough fun this year and decided to put a stop to it. The engine in the Boomers rod is a 1964 Buick “Nailhead”. I know, you want to know why they are called a nailhead. These engines use very small valves, which look like nails, so the term, “Nailhead”. Small valves mean small ports, which in those days lead to high torque, these engines can pull. Anyway, back to the story. The oil filter is held on the side of the engine with a small aluminum casting, an oil filter adapter. After forty five years of trouble free service, it decided to crack as soon as we took it to the racetrack. A very very small crack, that could not be seen when we removed the adapter to replace the gasket, thinking/hoping, it was just a gasket leak. Unfortunately it was not. As I am sure you can appreciate, an oil filter adapter for a forty five year old nailhead motor is not the easiest part to find, let alone in a small town like Ashcroft. We did consider trying epoxy, or some similar product, but because it is under pressure I simply didn’t want to take the chance. This weekend was all about fun, pumping oil out of the engine at half track is not fun. Add to that the nasty weather on Saturday. . . we went to the bakery for coffee.

The awards Banquet on Saturday night was great fun. It was a huge pleasure to surprise Dennis Hicks with a Wally of his own. When I won my Wally earlier this year, I ordered another so Dennis could have one, I felt he, as car owner, was as deserving of the award as me. So while I was up collecting my award for winning the series, I was able to thank my crew, and present Dennis with a trophy of his own. Thank you Dennis, for  the opportunity to drive your car. We will have another great season next year.

Sunday was spent saying goodbyes to everyone at the track, seeing everyone as often as we do through the summer means the next six months will be pretty quiet.

Well. . . not all that quiet. The shop is very busy, I have many articles planned for this blog, and a few other things in the works. A jet Funny car that needs some work for next season, and maybe a Nitro Dragster or two.

Writing

Well thank you to all of you. I am really enjoying this blog, learning how to watch it, and track it and such. I am sincerely flattered by the huge number of people who are out there looking for me specifically on Google or other search engines. And what is really cool as that when you find me, you read through my whole site, and then, even better, you keep on coming back. Thank you.

I will continue writing for you. I enjoy it. Sometimes I simply ramble on, like this morning, and of course other times I have something more specific to say. I have many ideas for articles that will be coming. I still intend to break the blog into three sections: a technical section, for the racers and fans who really want to get into the nuts and bolts of race cars. There will be what I like to call the personal growth section, in which I will discuss things mostly about my training and motivation. Things like meditation techniques I use, diet, exercise, and other things I use, or have tried or heard of, in that area. The third section will be about my own racing program. At this point I have two different cars lined up to drive next season, Dennis Hicks’ Mountain Brew dragster of course, and a jet funny car. I am also discussing options with two different top fuel teams, one running in IHRA out of Florida, and a local nostalgia top fuel car. So although the season is winding down for me, there will be plenty to watch out for.

This last week has been very busy on the phone and in meetings with team owners and sponsors, I apologize for not updating my blog as promptly as I would have liked.

By far the most popular articles I have written are the technical articles. I promise many more, starting with an in-depth how to on ladder bars and four links. The technical articles are much more involved to write. My objective is to make them as easy to read and understand as possible. I have yet to work out how to add decent drawings to my blog, so I may simply draw them then take a photo, probably much faster. It is also important to me that you are getting the correct information, in the correct order. So I will often do some research into specific details, which in turn leads me to a distraction, and hence it takes much longer to write a technical article. But they are coming, I promise. Of course if there are other technical subjects you would like to hear about, please, let me know. I will continue with the rear suspension theme for now. But there is very few aspects of the drag race car I cannot enlighten you on, from blown alcohol or nitro motor setup, clutch, carburetors too. Also things that one might consider simple, yet I often see them done incorrectly.

One thing in particular which was brought to my attention this weekend after a nasty incident, is the need for correct throttle linkage setups, with good strong toe hooks so the driver can pull the throttle back if he needs to. And in reality he should be pulling the throttle back whenever he closes it, not simply lifting his foot, but pulling back on it. As a driver, throttle control is very important to me. Having a correctly designed throttle linkage is mandatory if you want me to do a good job driving.

The unfortunate thing is that the small details do not get noticed until they are needed. And when they are needed is when it is a bad situation. When these cars are running right, when the tuneup is spot on, traction is ideal, they are almost easy to drive. It is when things are not right that you need all your ducks in a row, that toe hook on the throttle pedal only needs to work properly when the throttle is stuck open, until then you will never notice if it is strong enough or not. . . or will you. I hope you are off to the car right now to check on it.

Weekend update,

Sorry for the delay in getting this update posted.

The weekend was sweet and sour. The bad news is we only got two hits at the track and hurt our engine pretty bad on the second hit.

We are still searching for the correct combination of launch RPM, tire pressure, wheelie bar height, and torque converter to get a good launch with all the new horsepower we have with this new engine. The first run on Saturday morning was tough. With a low launch rpm we weren’t as close to the converter as we wanted to be, about three feet out from the line the engine and converter came on yanking the front wheels up hard, as a result hitting the wheelie bar hard. This sent the car into really good tire shake, eventually breaking the tires loose as the car skated over toward the wall. I pedalled it a little, settled the car, and drove it out the back door. Hit the chute lever, and it wasn’t there. Thought I might have missed it so tried again, no, it definitely isn’t there. Hard on the brakes, the car went into some serious bouncing. Neil, who was in the other lane tells me it was a good 18 inches, two feet in the air at times, bouncing from tire to tire. Have I told you how much fun these cars are to drive? I kept it off the walls, had one moment where I thought I might crash, but in the end I got it stopped. Neil said he could smell the brakes while he was still doing a hundred miles an hour behind me. Tire shake is a pretty violent thing, I guess when it shook early in the run it knocked the bolt out of the parachute lever. Back to the pits.

Rain interrupted the rest of the day, but we got another hit in the evening. We stepped up the launch RPM and added some more tire pressure. The car yarded the front tires right off the start line, shook into spin again and slid toward the centrline, same again, pedaled settled the car and hit it again. Had a parachute this time, but the car vibrated really bad in the shutdown and I knew something was seriously wrong.

We broke a tie bar between the roller lifters, the lifter turned in the bore so when the cam came around it broke the wheel off the bottom of the lifter, the wheel went down between the connecting rods and did some serious damage, not sure just how bad yet but there is a hole in the side of the block. When we get it further apart we will see just how bad it is. Nice thing with an aluminum block is that it can be welded up. We will be back.

Ok, that’s enough of the doom and gloom.

Uniforms! Tom and Debbie from CV Transport supplied us with some fantastic new crew shirts. The artwork is incredibly clear, and they look great next to the car. We were all strutting about very proud this weekend. Thank you Tom and Debbie.

Rear Suspension

This whole website is pretty cool. By watching the stats I can see that the most popular tags for searches which end up on my site is rear suspension setup, in particular four link setups.

I will, in the next couple weeks, publish a very in depth post on adjusting your four link correctly. It will be a long post to be sure I cover it properly. But to begin with, let’s cover some basics.

As I am sure you have deduced, I am a drag racer, so this discussion refers to drag racing setups. If you want info for a street setup, or something to go around corners, send me an email and I can help you individually.

Let’s start with some basic high school physics. Newton’s law of motion states that for every action there is an equal and opposite reaction. This applies to almost everything we are doing while trying to accelerate a car down the quarter mile, and is very handy to remember when designing or modifying anything on the car.

Pistons are pushing down on the connecting rods, and the crankshaft, most of us understand that, but what are they pushing against? They push up against the cylinder heads, and, here it comes, they push up the same amount that they are pushing down, Newton got it right. That is an example for you, back to the rear suspension.

Your driveshaft is rotating, clockwise when viewed from the front. This turns the pinion gear in the front of your rear axle, the pinion gear is meshed with the ring gear, turning the rotation ninety degrees to drive the rear wheels. Try to picture the following, it can be tricky, but once you get it you will have a better understanding of what is happening in the rear suspension. As the pinion gear is rotating, meshed with the ring gear, if the slicks are stuck hard to the track, in effect preventing the ring gear from turning, or at least impeding the ring gear from turning, the pinion gear is literally trying to “climb up” the ring gear. Picture the ring gear as stationary, the pinion then climbs up the ring. Back to Newton, even when the tires start to rotate as the car accelerates forward, the pinion gear is still trying to climb up the ring gear, by an equal amount of force. Equal to, and opposite the amount of force trying to drive the car forward, (ok, there are some minute losses, friction and such, but for this discussion we can forget about them). And it is a huge amount of force, (torque). Think about that 750 ft lbs of torque your engine makes, multiplied through the torque converter, before hitting your first gearset which multiplies it even more, it is a huge amount of torque, (I am saving the calculations for another post). Now if the pinion is trying to climb up the ring gear, what is stopping it? The axle housing stops it, and in turn, whatever is holding the axle housing in the car. . . four links, ladder bar, leaf spring, etc.

Now, rather than visualizing the pinion climbing the ring gear, picture the whole axle housing trying to rotate up and around the rear axle, in the opposite direction to tire rotation, (and with an equal amount of force, Newton again). The housing is being driven around the rear axle by the pinion gear. It is this rotational force that we are harnessing with a four link or ladder bar or any other rear suspension setup.

A four link has two bars per side, a top bar and bottom bar. Pictured from the side, and under acceleration, (people often forget that under braking, or deceleration, everything happens the other way, ever see a car try to turn when backing off at the top end?), the bottom bar is being pushed forward, and being compressed by the rotational force of the axle housing, while the top bar is being pulled backwards and upwards in tension, trying to lift the chassis of the car. Adjusting the angle of the bars, controls the direction of the push and the pull, pushing the car forward, pulling up on the chassis, lifting the chassis, in turn transferring weight to the rear tires.

This all refers to the basic load directions in a four link rear suspension, so that you can picture what is happening back there when you release the trans brake, or mash the throttle. I have tried to make it basic enough to follow, yet assume the reader has a bit of an understanding of the terms I am using. These loads are all similar in a ladder bar setup, or leaf springs. Stock coil spring rear end setups, like some Mustangs and Camaros are in one form or another a four link, but with different geometry for anti-squat and anti-dive, as well as general passenger comfort. This is the first time I have ever really written a technical article, and hope I am making the concepts clear and understandable. I will work out how to add drawings in future articles to help clarify some of the concepts. If you have any questions, don’t quite understand what it is I am trying to get across, or want some clarification, please send me an email, I would love to hear. If you have any ideas for future posts, I would love to hear them too.

I will continue this discussion on rear suspensions soon, so check back often.

Ladder bars.

Why not a four link?

I am a big fan of ladder bars. For the majority of racers out there a ladder bar will do everything they require. But a four link is better, I hear this all the time, and yes in some perspectives a four link is a much better drag racing rear suspension setup. The biggest advantage to a four link is it’s adjust-ability.  This can be a great advantage. . .  if you know how to adjust it. When I look around the track, I see very few people adjusting their four links. Generally what I see are four links that have been setup, either by someone who knows how to tune them, or after a certain amount of aggravation, or “that’s how I bought the car, and I am not going to touch it ’cause it is working just fine the way it is”., and because the car is going straight, and running consistent, the owner leaves it alone.

The problem with a four link is that very few people have spent the time to work out how to make adjustments. I am not going to get into how to adjust a four link here, but I will tell you that the procedure starts when the car is being built. The chassis builder should have given you a chart of instant centres. If you don’t have one, you need to get one. You can generate one yourself. There are computer programs you can buy that make it easier, or you can do it the old fashioned way on the floor. I have done both. I now have a computer program I find reasonably easy to use although it does not allow for as many holes as we are using in newer four link setups, so I have to run the program twice. Once you have your instant centre chart, you then need some sort of preload reference. How much weight, does a quarter turn on the bar add, or subtract, form each corner. Of course this will change with a change in instant centre, so if you change bar locations, you then need to know the preload adjustments for that location. The point I am trying to make here is that although a four link is a great rear suspension setup, the adjustment procedure is too involved many drag racers. They generally get it working, then never adjust it.

If that is going to be the case, why not use a ladder bar then? A ladder bar generally has three choices for instant centre, and you can see them all on the car, you don’t need a chart. Preload can be set with a ruler if you want, although I do prefer to weigh the car so I have a reference point for preload adjustments. Often, unless it is a very high horsepower car, little or no preload is required with a ladder bar.

Ladder bars do take up a little more space forward in the chassis, if you are building a car with a lot of rearward driver position it can be a challenge to get a long enough bar in the car.

One of the cars I am currently building is a ladder bar setup. It is a very short wheelbase at 100.5 inches, so getting bars in there can be done. This one is interesting in that the owner wanted to use his rear axle housing which was already setup for a four link. It has a range of holes on the axle housing that could be used, and they are not in the usual location for a ladder bar. I had to get creative. One problem the typical ladder bar has is because of the angle of the two bars, as soon as you adjust the rear of the bar for pinion angle, the hole spacing changes, causing a side load on the rod ends, this is not good at all. It can also cause a certain amount of stress and cursing when trying to install the bars after making an adjustment.

For this car, I wanted to take advantage of the range of holes in the housing. I accomplished this by putting a pivot in the top tube, allowing the hole spacing at the rear to be adjustable. This solves two problems, first there is now no side loading on the rear rod ends after adjustment, and second, because I made the top bar adjustable, pinion angle can be changed very easily. Now that I have built these bars, I wouldn’t build them any other way. They are a little more expensive, but worth it. They offer a large range of adjust-ability, without the confusion of a four link. They are very strong, with large diameter thick wall 4130 tubing. And they can be built to suit any set of brackets you may already have.

Questions? Ask away, at the contacts page

Since I published this post a few days ago, it is interesting to note that people are finding it when searching “how to adjust four links”. I will compose an in depth look at how to adjust a four link suspension for future post. It may take a while so check back often. If you have any specific questions concerning your setup, my email is on my contacts page.